1. Field
Many aspects of this disclosure relate to a deflectable catheter assembly having a compression compensation mechanism. The catheter assembly of an exemplary embodiment includes a deflectable distal section, a non-deflectable section, a proximal catheter handle, and a tool (e.g., a needle, a therapeutic device, and a diagnostic device), and a compression compensation mechanism coupled to the tool.
2. Discussion of Related Art
Steerable catheters have been commonly used in applications such as mapping (e.g., cardiac mapping), drug delivery (e.g., intramyocardial drug delivery), and ablation, (e.g., arrhythmia ablation).
A steerable catheter has a deflectable flexible distal section and a stiffer proximal torqueable shaft. The steerable function is accomplished by three modes of actions: 1) translational catheter movement along the shaft direction, 2) deflection of the distal deflectable section, and 3) turning of the catheter shaft to direct the deflection toward the target therapy site. A tendon wire is included to control the deflection of the distal section. This tendon wire is located inside of a sheath running along and within the catheter shaft with its distal end attached near the distal tip of the catheter. A pulling mechanism is included within the proximal catheter handle, which is coupled to the proximal end of the catheter shaft. The pulling mechanism controls the tendon wire to deflect the distal section of the catheter shaft. Radially, the tendon wire is located off-center of the catheter shaft center to create a moment toward the intended deflection side in the catheter distal deflectable section. When the tendon wire is pulled, the catheter deflects toward the radial direction to which the tendon wire is located. The deflection section is typically made to be much more flexible than the rest of the catheter shaft. When the tendon wire is pulled in tension, the catheter shaft wants to “curl up.” The distal section is the most flexible section of the catheter shaft and thus it deflects when the tendon wire is pulled. To direct the deflected section toward the target site, an operator turns the catheter shaft on the proximal end. The deflection section responds to the torque in a fashion that is governed by the way the catheter is constructed.
Depending on the therapeutic use of the catheter, a therapeutic tool, such as a needle, may run in parallel to the tendon wire within the catheter shaft.
Deflectable catheters have been in common use in medical practice for many years. The catheters are used to probe locations inside a body lumen that are otherwise unreachable without surgery. A catheter is inserted into a major vein or artery, or other body lumen that is near the body surface, possibly with the aid of an introducer entering the body lumen and a guide catheter previously inserted.
The catheter is then guided to the area of concern by inserting the catheter further into the body lumen. As medical knowledge increases, catheterizations have become more complicated and exacting. In many situations the ability to control the position and orientation of the catheter tip may largely determine the usefulness of the catheter.
In a steerable catheter, deflecting the distal tip of the catheter to a bent shape causes the outer catheter body or shaft to undergo some compression and some shortening in length. Devices internal to the catheter body (e.g., a needle assembly) and not connected directly to the catheter body do not change in length, or at least do not change in length as much, when the distal tip of the catheter is deflected. The internal devices thus become longer relative to the outer catheter body. This change in relative length can affect the deployment of the internal devices. For instances, a needle may extend longer than anticipated due to the compression. The needle is thus not in the expected position which may require the operator/physician to have to make further adjustment.